1. Field of the Invention
This invention relates to a radiation clinical thermometer, and more particularly to an improved radiation clinical thermometer for measuring human body temperature by sensing infrared radiation.
2. Discussion of the Related Art
A conventional radiation clinical thermometer includes a body housing enclosing circuitry and a power source, a probe externally projecting from the housing and internally enclosing an infrared radiation sensor (temperature sensor), and a probe switch. The sensor is designed to collect infrared radiation through the probe. An example of such a conventional radiation clinical thermometer is disclosed in U.S. Pat. No. 4,895,164. For the measurement of a body temperature, the conventional radiation clinical thermometer is used by inserting its probe into an ear opening. When the thermometer is not in use, a cap is mounted on the probe. For the prevention of stains and for sanitation purposes, the probe is mounted by a probe cover for use in measuring.
Conventional clinical thermometers have the disadvantage that unnecessary measurement is initiated upon the depression of a start switch even if a probe cover is not mounted on the probe. If a probe cover is mounted on the probe in the power-on state of a conventional radiation clinical thermometer which is designed to actuate the temperature measuring start switch in response to the movement of the probe, the probe moves backwardly as the probe is pushed into the ear opening. The backward movement of the probe turns on the probe start switch for immediate measurement of body temperature. If, however, during the power on state of the thermometer, the probe is unintentionally pushed when the cover is not mounted thereon, or is pushed backwardly in the process of the probe cover being mounted thereon, temperature measurement is initiated so as to execute an unnecessary measurement of body temperature in spite of the unmounted state of the cover. Such initiation of measurement by unintentionally depressing the probe is prevented if the cover is carefully and precisely mounted. However, it is often the case that mounting is carelessly executed and unnecessary temperature measurement occurs. Since the temperature measurement circuitry is designed to operate to take into account the attenuation of the infrared radiation by the cover, if no cover is used, the thermometer will display a temperature measurement result that is higher than the actual temperature so that a precise body temperature measurement is not obtained.